The theft of parked semitrailers loaded with merchandise is lucrative business for thieves and costly for the owners of the merchandise.
Short of parking loaded semitrailers in guarded, impenetrable compounds, the best theft deterrent thus far devised has been a locking mechanism for the king pin of the trailer which prevents the pin from being engaged by the fifth wheel mechanism on a tractor. And, several inventors have devised locking mechanisms for this purpose.
Representative king pin locking mechanisms are disclosed in U.S. Pat. Nos. 3,798,938, granted Mar. 26, 1974, to R. G. McCullum, for "ARMORED LOCK MECHANISM", 3,922,897, granted Dec. 2, 1975, to T. J. Mickelson for "SEMITRAILER KING PIN SECURING DEVICE", and 4,697,444, granted Oct. 6, 1987, to C. O. Maffey for "SECURITY DEVICE FOR TRAILER".
Unfortunately, a sophisticated thief or team of thieves can, given sufficient time, defeat these prior locking mechanisms. The attack on the locking mechanism may involve one or more of the following techniques: drilling; punching; embrittlement by cryogenic treatment; cutting with oxy-acetylene torch, an abrasive wheel, a band saw, or a hydraulic splitter; ballistic destruction; and cylinder lock manipulation. In most attacks, the objective is to disable or destroy the key actuated cylinder lock to permit the locking mechanism to be released from the semitrailer king pin. Each of the McCullum, Mickelson and Maffey locking mechanisms can be disabled in this manner.
Another theft technique is to equip the tractor with a modified fifth wheel mechanism that includes a clamp for grasping the housing for the locking mechanism so that the trailer can be hauled away with the locking mechanism still in place. Neither McCullum, Mickelson or Maffey offers a solution to this type theft. There continues to be a need for a reliable king pin locking mechanism capable of thwarting these various attack techniques.